Ion beam processing apparatus, electrode assembly, and method of cleaning electrode assembly

ABSTRACT

Provided is an ion beam processing apparatus including an ion generation chamber, a processing chamber, and electrodes to form an ion beam by extracting ions generated in the ion generation chamber to the processing chamber. The electrodes includes a first electrode disposed close to the ion generation chamber and provided with an ion passage hole to allow passage of the ions, and a second electrode disposed adjacent to the first electrode and closer to the processing chamber than the first electrode is, and provided with an ion passage hole to allow passage of the ions. The apparatus also includes a power unit which applies different electric potentials to the first electrode and the second electrode, respectively, so as to accelerate the ions generated by an ion generator in the ion generation chamber. A material of the first electrode is different from a material of the second electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/878,206, filed Oct. 8, 2015, which is a continuationapplication of International Application No. PCT/JP2013/007269, filedDec. 10, 2013, which claims the benefit of Japanese Patent ApplicationNo. 2013-088656 filed Apr. 19, 2013. The contents of the aforementionedapplications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an ion beam processing apparatus, anelectrode assembly, and a method of cleaning an electrode assembly.

BACKGROUND ART

Processing using an ion beam is performed in manufacturing of variouselectronic components and the like. In particular, an ion implantationapparatus for implanting an impurity into semiconductor, an ion beametching apparatus (hereinafter abbreviated as an IBE apparatus)configured to process a substrate by irradiating the substrate with anion beam, and the like are widely used. Such an ion beam processingapparatus includes: an ion generation chamber being configured togenerate plasma and thus serving as an ion source; a processing chamberin which a substrate is mounted on a holder and is subjected toprocessing; and an electrode assembly provided between the iongeneration chamber and the processing chamber and configured to extractions. The electrode assembly includes three electrodes each providedwith numerous ion passage holes, and is known to use Mo (molybdenum),which is excellent in heat resistance and sputtering resistance, as thematerial thereof (see Patent Document 1).

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-118290

Non Patent Documents

Non Patent Document 1: “Chronological Scientific Tables 2001”, p. 475,Edited by National Astronomical Observatory of Japan, Published on Nov.30, 2000 by Maruzen Co., Ltd.

Non Patent Document 2: “P. G. Pyrolytic Graphite”, (online), TomoeEngineering Co. Ltd., (Searched on Apr. 9, 2013) on the Internet (URL:http://www.tomo-e.co.jp/cmsfiles/product/i-707724-rl.pdf)

Non Patent Document 3: “Iron-nickel Alloy”, (online), Hitachi Metals,Ltd., (Searched on Apr. 6, 2013) on the Internet (URL:http://www.hitachi-metals.co.jp./prod/prod01/pdf/hando_bra.pdf)

SUMMARY OF INVENTION

As described in Patent Document 1, the electrode assembly in the IBEapparatus includes at least three electrodes, namely, a first electrodeto which a positive voltage is applied, a second electrode to which anegative voltage is applied, and a third electrode at ground potential.Here, each of these electrodes is known to use Mo as its material.

When a substrate is subjected to etching with an ion beam by using theabove-described IBE apparatus, ions flowing out of the plasma in the iongeneration chamber to the electrode assembly are accelerated by avoltage difference between the first electrode and the second electrode.The accelerated ions pass through the ion passage holes provided in theelectrodes included in the electrode assembly, and are thus emitted asan ion beam into the processing chamber. However, part of theaccelerated ions cannot pass through the ion passage holes, andtherefore collide with the second electrode while retaining largeenergy. For this reason, portions around the ion passage holes of thesecond electrode are significantly etched, in particular, in associationwith the use of the IBE apparatus. At this time, the substance of thesecond electrode scattered from the second electrode mainly adheres to aportion of the first electrode facing the second electrode (the portionnot facing the plasma).

Such an adhering matter to the first electrode can be removed bycleaning. However, since the material of the first electrode is the sameas the material of the second electrode in the conventional apparatus,there is strong adhesion between the first electrode and the substancescattered from the second electrode and adhering onto the firstelectrode, and it is therefore difficult to detach this adhering matterin a cleaning process. Moreover, since the first electrode and thesecond electrode are made of the same material, it is not possible toselectively remove the adhering matter by utilizing reactivity in thecleaning process. Instead, the adhering matter needs to be removed by aphysical processing method such as blasting. When the removal by thephysical method is performed, a mechanical force is applied to theelectrode. As a consequence, the electrode is deformed by the repetitionof the cleaning process. Accordingly, there is also a problem that thelife of the electrode is reduced and it is difficult to use theelectrode repeatedly.

The present invention has been made in view of the above-mentionedproblems. The conventional ion beam processing apparatus has the problemthat the adhering matter containing the substance of the secondelectrode, to which the negative voltage is applied, adheres to thefirst electrode, to which the positive voltage is applied, in the casewhere the electrodes are included in the electrode assembly of the ionbeam processing apparatus. In view of the above, it is an object of thepresent invention to provide an ion beam processing apparatus, anelectrode assembly, and a method of cleaning an electrode assembly whichare capable of selectively removing such an adhering matter by utilizingreactivity.

To attain the object, a first aspect of the present invention providesan ion beam processing apparatus configured to perform processing by ionbeam irradiation, which includes: an ion generation chamber including anion generator; a processing chamber in which the processing is performedand a holder to hold a substrate is disposed; multiple electrodesconfigured to separate the ion generation chamber from the processingchamber, and to form an ion beam by extracting ions generated in the iongeneration chamber to the processing chamber, the multiple electrodesincluding a first electrode disposed close to the ion generation chamberand provided with an ion passage hole to allow passage of the ions, anda second electrode disposed adjacent to the first electrode and closerto the processing chamber than the first electrode is, and provided withan ion passage hole to allow passage of the ions; and a power unitconfigured to apply different electric potentials to the first electrodeand the second electrode, respectively, so as to accelerate the ionsgenerated by the ion generator in the ion generation chamber. Here, amaterial of the first electrode is different from a material of thesecond electrode, and a linear expansion coefficient α₁ of the materialof the first electrode and a linear expansion coefficient α₂ of thematerial of the second electrode satisfy a relation of α₁<α₂.

A second aspect of the present invention provides an ion beam processingapparatus configured to perform processing by ion beam irradiation,which includes: an ion generation chamber including an ion generator; aprocessing chamber in which the processing is performed and a holder tohold a substrate is disposed; multiple electrodes configured to separatethe ion generation chamber from the processing chamber, and to form anion beam by extracting ions generated in the ion generation chamber tothe processing chamber, the multiple electrodes including a firstelectrode disposed close to the ion generation chamber and provided withan ion passage hole to allow passage of the ions, and a second electrodedisposed adjacent to the first electrode and closer to the processingchamber than the first electrode is, and provided with an ion passagehole to allow passage of the ions; and a power unit configured to applydifferent electric potentials to the first electrode and the secondelectrode, respectively, so as to accelerate the ions generated by theion generator in the ion generation chamber. Here, a material of thefirst electrode is different from a material of the second electrode. Inaddition, the ion beam processing apparatus further includes a thirdelectrode disposed closer to the processing chamber than the secondelectrode is. Here, an electric potential, which is different from theelectric potentials to be applied to the first electrode and the secondelectrode, is applied to the third electrode. Moreover, a material ofthe third electrode is different from the material of the secondelectrode.

A third aspect of the present invention provides an ion beam processingapparatus configured to perform processing by ion beam irradiation,which includes: an ion generation chamber including an ion generator; aprocessing chamber in which the processing is performed and a holder tohold a substrate is disposed; multiple electrodes configured to separatethe ion generation chamber from the processing chamber, and to form anion beam by extracting ions generated in the ion generation chamber tothe processing chamber, the multiple electrodes including a firstelectrode disposed close to the ion generation chamber and provided withan ion passage hole to allow passage of the ions, and a second electrodedisposed adjacent to the first electrode and closer to the processingchamber than the first electrode is, and provided with an ion passagehole to allow passage of the ions; and a power unit configured to applydifferent electric potentials to the first electrode and the secondelectrode, respectively, so as to accelerate the ions generated by theion generator in the ion generation chamber. Here, a material of thefirst electrode is different from a material of the second electrode.The multiple electrodes include multiple flat plate electrodes. Here,each of the multiple flat plate electrodes includes numerous ion passageholes to allow passage of the ions. Moreover, positions of the ionpassage holes in the flat plate electrodes and linear expansioncoefficients of the materials of the flat plate electrodes are set suchthat, at the time of non-irradiation of the ion beam, each ion passagehole in one of the flat plate electrodes is located at such a positionnot coinciding with the corresponding ion passage hole in the other flatplate electrode in terms of a planar direction when viewed from aperpendicular direction, and at the time of irradiation of the ion beam,the ion passage hole in the one flat plate electrode moves from theposition at the time of non-irradiation in such a direction to coincidewith the corresponding ion passage hole in the other flat plateelectrode in the planar direction by thermal expansion attributed to arise in temperature.

A fourth aspect of the present invention provides a method of cleaning afirst electrode included in an ion beam processing apparatus, which isconfigured to perform processing by ion beam irradiation, and providedwith: an ion generation chamber including an ion generator; a processingchamber in which the processing is performed and a holder to hold asubstrate is disposed; multiple electrodes configured to separate theion generation chamber from the processing chamber, and to form an ionbeam by extracting ions generated in the ion generation chamber to theprocessing chamber, the multiple electrodes including the firstelectrode disposed close to the ion generation chamber and provided withan ion passage hole to allow passage of the ions, and a second electrodedisposed adjacent to the first electrode and closer to the processingchamber than the first electrode is, and provided with an ion passagehole to allow passage of the ions; and a power unit configured to applydifferent electric potentials to the first electrode and the secondelectrode, respectively, so as to accelerate the ions generated by theion generator in the ion generation chamber. Moreover, a material of thefirst electrode is different from a material of the second electrode.Here, the method includes the steps of: preparing a cleaning agenthaving a rate to dissolve the material of the second electrode beinghigher than a rate to dissolve the material of the first electrode; andremoving the material of the second electrode adhering to the firstelectrode from the first electrode by bringing the material of thesecond electrode into a reaction with the cleaning agent.

A fifth aspect of the present invention provides an electrode assemblyincluded in the ion beam processing apparatus of the first aspect of thepresent invention and being a subject of the cleaning method of thefourth aspect of the present invention. The electrode assembly isconfigured to extract ions from an ion source and to form an ion beam,and includes: multiple electrodes, including a first electrode disposedon the ion source side and provided with an ion passage hole to allowpassage of the ions, and a second electrode disposed on an opposite sideof the first electrode from the ion source and provided with an ionpassage hole to allow passage of the ions. Here, a material of the firstelectrode is different from a material of the second electrode.

A sixth aspect of the present invention provides an ion beam processingapparatus configured to perform processing by ion beam irradiation,which includes: an ion generation chamber including an ion generator; aprocessing chamber in which the processing is performed and a holder tohold a substrate is disposed; multiple electrodes configured to separatethe ion generation chamber from the processing chamber, and to form anion beam by extracting ions generated in the ion generation chamber tothe processing chamber, the multiple electrodes including a firstelectrode disposed close to the ion generation chamber and provided withan ion passage hole to allow passage of the ions, and a second electrodedisposed adjacent to the first electrode and closer to the processingchamber than the first electrode is, and provided with an ion passagehole to allow passage of the ions; and a power unit configured to applydifferent electric potentials to the first electrode and the secondelectrode, respectively, so as to accelerate the ions generated by theion generator in the ion generation chamber. Here, a material of thefirst electrode is different from a material of the second electrode.Meanwhile, the first electrode contains titanium, and the secondelectrode contains pyrolytic graphite.

According to the ion beam processing apparatus, the cleaning method, andthe electrode assembly of the present invention, it is possible toprovide an ion beam processing apparatus, an electrode assembly, and amethod of cleaning an electrode assembly which are capable of utilizingreactivity and thereby selectively removing an adhering matter in thecase where the adhering matter containing a material of a secondelectrode, which is located closer to a processing chamber and adjacentto a first electrode that is located on an ion generation chamber side,adheres to the first electrode due to use of an ion beam processingapparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an IBE apparatus as an example of aprocessing apparatus according to an embodiment of the presentinvention.

FIG. 2 is a schematic diagram of an electrode assembly constituting partof the IBE apparatus according to the embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below withreference to the drawings. It is to be noted, however, that the presentinvention is not limited to this embodiment and various changes arepossible within the scope not departing from the gist of the invention.It is to be also noted that in the following explanation made inconjunction with the drawings, portions having the same functions willbe denoted by the same reference numerals and repetitive descriptionsthereof may be omitted when appropriate.

FIG. 1 illustrates a schematic diagram of an IBE apparatus as an exampleof an ion beam processing apparatus of this embodiment. A configurationof the ion beam processing apparatus will be described.

An IBE apparatus 100 includes an ion generation chamber 102 and aprocessing chamber 101.

As a plasma formation system for forming plasma in the ion generationchamber 102, a bell jar (a discharge vessel) 104, a gas introductionpart 105, and an antenna 106 that includes a conductive member and isconfigured to generate an induced magnetic field in the bell jar 104 areinstalled in the ion generation chamber 102. Outside the bell jar 104there are also installed a discharge power unit 112 configured to supplyhigh-frequency power (source power) to the antenna 106, a matchingnetwork 107 provided between the discharge power unit 112 and theantenna 106, and an electromagnetic coil 108. The bell jar 104 is partof a chamber external wall that keeps a vacuum in the ion generationchamber 102 as well as in the processing chamber 101, which is also avessel to encapsulate the plasma generated by electric discharge. Thehigh-frequency power supplied from the discharge power unit 112 is fedto the antenna 106, whereby the plasma is formed in the ion generationchamber 102 inside the bell jar 104.

The processing chamber 101 includes: a neutralizer 113 which neutralizesan ion beam; a substrate holder 110 serving as a holder to hold asubstrate 111 which is a subject to be processed; and a vacuum pump 103which removes the air inside the ion generation chamber 102 and theprocessing chamber 101 and keeps the inside in vacuum. A not-illustratedelectrostatic chuck (ESC) electrode is connected to the substrate holder110. By this ESC electrode, the substrate 111 mounted on the substrateholder 110 is fixed thereto by means of electrostatic attraction. Notethat the substrate holder 110 only needs to have a function to fix thesubstrate and does not always have to utilize the electrostaticattraction attributed to the ESC electrode. Various substrate fixationmethods, including one involving a clamp chuck, for example, can be usedherein.

An electrode assembly 109 provided with ion passage holes for extractingions is disposed at a boundary that separates the ion generation chamber102 from the processing chamber 101. FIG. 2 illustrates a schematicdiagram of the electrode assembly 109.

The electrode assembly 109 includes multiple pieces of flat plateelectrodes each provided with a hole serving as the ion passage hole.Although one ion passage hole is illustrated on each of the flat plateelectrodes in the drawing, numerous similar ion passage holes may byarranged instead. For example, numerous ion passage holes may bearranged in a matrix and in a grid (lattice) fashion. As illustrated inFIG. 2, the electrode assembly 109 includes a first electrode 70, asecond electrode 71, and a third electrode 72 which are arranged fromthe ion generation chamber 102 side toward the processing chamber 101side. Specifically, the first electrode 70 is disposed closest to theion generation chamber side, i.e., an ion source side, while the secondelectrode 71 is disposed adjacent to the first electrode 70 and closerto the processing chamber 101 than the first electrode 70 is. Meanwhile,the third electrode 72 is disposed closest to the processing chamber101. A voltage source 73 and a voltage source 74 are connected to thefirst electrode 70 and the second electrode 71, respectively, whereby apositive voltage is applied to the first electrode and a negativevoltage is applied to the second electrode. Thus, a potential differencefor accelerating the ions is generated between the first electrode andthe second electrode. The third electrode 72 is electrically grounded. Adiameter of the ion beam can be controlled within a predetermined rangeof numerical values using an electrostatic lens effect, by controlling apotential difference between the second electrode 71 and the thirdelectrode 72.

An operation of ion beam irradiation using the IBE apparatus 100 will bedescribed. First, a process gas containing an inert gas such as argon(Ar) is introduced from the gas introduction part 105 into the iongeneration chamber 102. Next, the process gas inside the ion generationchamber 102 is ionized by applying a high-frequency wave from thedischarge power unit 112 to the antenna 106, and the ion source isprepared by generating plasma 75 that contains the ions. The ionscontained in the plasma 75 generated in the ion generation chamber 102are accelerated by the potential difference provided between the firstelectrode 70 and the second electrode 71 when the ions pass through thenumerous ion passage holes provided in the electrode assembly 109. Then,the ions are extracted as an ion beam 76 to the processing chamber 101.The ion beam is extracted to the processing chamber 101, and is thenneutralized by the neutralizer 113 and emitted onto the substrate 111.Thus, a surface of the substrate 111 is subjected to etching.

As described previously, when the ions attempt to pass through the ionpassage holes provided in the electrodes included in the electrodeassembly 109, part of the accelerated ions cannot pass through the ionpassage holes and collide with the second electrode while retaininglarge energy. For this reason, portions around the ion passage holes ofthe second electrode 71 are significantly etched, in particular, as theIBE apparatus 100 is used. At this time, the substance of the secondelectrode 71 scattered from the second electrode 71 mainly adheres to aportion of the first electrode 70 facing the second electrode 71 (theportion not facing the plasma 75). Such an adhering matter causesadverse effects on stability of the ion beam processing including achange in diameter of each ion passage hole in the first electrode 70,and the like. Therefore, the adhering matter needs to be removedregularly. For this reason, a cleaning process is performed on theelectrode assembly 109 after the ion beam processing. Regarding detailsand cleaning of the electrode assembly 109, specific examples will bediscussed below.

First Embodiment

In this embodiment, the material of the first electrode 70 is molybdenum(Mo) while the material of the second electrode 71 is titanium (Ti). Itis to be noted that, in this embodiment, the description “the materialof the first electrode 70 is Mo” does not intend to exclude elementsother than Mo, compounds thereof, and the like. In this context, thefirst electrode 70 may contain components (elements, compounds,impurities, and the like) other than Mo as long as the first electrode70 can fulfill the function to apply the positive voltage foraccelerating the ions in the electrode assembly 109. In other words, inthis embodiment, it is possible to say that the first electrode 70contains Mo as its major component. In the meantime, the description“the material of the second electrode 71 is Ti” does not intend toexclude elements other than Ti, compounds thereof, and the like. In thiscontext, the second electrode 71 may contain components (elements,compounds, impurities, and the like) other than Ti as long as the secondelectrode 71 can fulfill the function to apply the negative voltage foraccelerating the ions in the electrode assembly 109. In other words, inthis embodiment, it is possible to say that the second electrode 71contains Ti as its major component.

It is to be noted that, when a description “a material of a certainelectrode is a certain substance” is made in this specification, thedescription means that the certain electrode may also contain components(elements, compounds, impurities, and the like) other than the certainsubstance.

In this embodiment, when the ion beam processing is performed, thesecond electrode 71 may be etched by the ions extracted from the plasma75 and Ti being the material of the second electrode 71 may be scatteredby the etching. As a consequence of this scatter, Ti being the materialof the second electrode 71 adheres to a surface of the first electrode70 which uses Mo as its material. In the meantime, Ti has a propertythat its dissolution rate to a solution such as hydrofluoric acid ishigher than that of Mo. Accordingly, Ti out of Mo and Ti is selectivelydissolved by use of this property while cleaning the first electrode 70by employing the solution such as hydrofluoric acid as a cleaning agent.As a consequence, Ti adhering to the first electrode 70 due to theetching of the second electrode 71 can be selectively removed. Asdescribed above, by forming the second electrode 71 from the materialdifferent from that of the first electrode 70, the adhering matter thatadheres due to the ion beam processing can be removed by the selectiveetching. This makes it possible to conduct chemical processing withoutapplication of a mechanical force. Accordingly, the deformation of theelectrode assembly 109, which has been a problem of conventionalphysical processing such as the blasting, is either reduced oreliminated. Hence, there is an advantage that the electrode assembly 109has an extended product life and can be used repeatedly. In other words,it is possible to successfully remove the adhering matter originatingfrom the second electrode 71 adhering to the first electrode 70, withoutcleaning the first electrode 70 by the physical method such as theblasting.

While the material of the second electrode 71 etched and scattered bythe ion beam processing mainly adheres to the first electrode 70, partof the material also adheres to the third electrode 72. Accordingly, itis also preferable to form the third electrode 72 from a materialdifferent from that of the second electrode 71. Thus, as with thecleaning of the first electrode 70, the third electrode 72 can also becleaned by use of a solution which is capable of selectively dissolvingthe adhering matter. Hence, the third electrode 72 can be cleanedeasily. Furthermore, by forming the third electrode 72 from the samematerial as that of the first electrode 70, it is possible to clean theelectrode assembly 109 by identical processing to that applicable to thefirst electrode 70. It is also possible to perform the cleaningsimultaneously in order to simplify the process. To be more precise, thematerial of the first electrode 70 and the third electrode 72 may be Mowhile the material of the second electrode 71 may be Ti, for example.Thus, it is possible to remove Ti adhering to the first electrode 70 andthe third electrode 72 by using the hydrofluoric acid solution.

At this time, detachment of the adhering matter containing the substanceof the second electrode 71 and adhering onto the first electrode 70 canbe reduced by bringing a thermal expansion of the material of the firstelectrode 70 closer to a thermal expansion of the material of the secondelectrode 71. This point will be specifically discussed below.

The substance scattered from the second electrode 71 adheres mainly to asurface (a surface on the processing chamber 101 side) of the firstelectrode 70 on an opposite side from a surface in contact with theplasma 75. Here, the first electrode 70 in direct contact with theplasma 75 receives energy of the plasma 75. In other words, this side ofthe first electrode 70 is likely to be heated more than is the adheringmatter, which is located on the surface of the first electrode 70 on theprocessing chamber 101 side and is therefore not in direct contact withthe plasma 75. As a consequence, the first electrode 70 becomes higherin temperature than the adhering matter. For this reason, if thematerial of the first electrode 70 and the material of the secondelectrode 71, i.e., the material of the adhering matter have the samelinear expansion coefficient, then the thermal expansion (=linearexpansion coefficient×amount of rise in temperature) of the firstelectrode 70 becomes greater than that of the adhering matter.

Here, the linear expansion coefficient means a rate of change of lengthwith respect to temperature per unit length, which is also referred toas a linear expansion rate, a thermal expansion rate, and so forth. Thelinear expansion coefficient is a constant unique to each material, andthe linear expansion coefficient of each electrode is determined bydeciding the material.

When the thermal expansion of the first electrode 70 is greater than thethermal expansion of the adhering matter that adheres to the firstelectrode 70, a large stress is applied to the adhering matter. If thestress applied to the adhering matter is large, the adhering matter maybe detached and scattered from the first electrode 70, and may adhere tothe substrate 111 and generate particles. Such particles may lead tooccurrence of a defect such as disconnection in the production ofsemiconductor circuit elements in which fine patterns are formed.

Accordingly, in this embodiment, the linear expansion coefficient of thefirst electrode 70 is preferably set smaller than the linear expansioncoefficient of the second electrode 71. Specifically, the linearexpansion coefficient α₁ of the first electrode 70 and the linearexpansion coefficient α₂ of the second electrode 71 preferably satisfy arelation of α₁<α₂. In this way, the thermal expansion of the firstelectrode 70 is brought closer to the thermal expansion of the adheringmatter adhering to the first electrode 70. Thus, the detachment of theadhering matter can be reduced by diminishing the stress appliedthereto, and the particles that adhere to the substrate 111 are reducedas well.

As examples of combinations of the materials, if Mo is used for thefirst electrode 70, then any of Ti, a nickel-iron alloy (NiFe alloy),tungsten (W), tantalum (Ta), and the like is used as the secondelectrode 71. Meanwhile, when Ti is used for the second electrode 71, Moor a carbon-based material such as pyrolytic graphite (PG) is used asthe material of the first electrode 70. By selecting these materials asappropriate, it is possible to achieve the above-mentioned relation ofthe thermal expansions and thus to obtain the above-mentioned effect.

Table 1 describes values of the linear expansion coefficients as well assputtering rates to be described later. Here, codes such as “*(1)” inthe table represent the documents (Non Patent Documents 1 to 3) fromwhich the values are cited.

TABLE 1 NiFe Item PG Mo W Ta Ti alloy Ni Linear 0.6*⁽²⁾ 3.7-5.3*⁽¹⁾4.5*⁽¹⁾ 6.3*⁽¹⁾ 8.6*⁽¹⁾ 4.5-5.3*⁽³⁾ 13.4*⁽¹⁾ Expansion Coefficient(10⁻⁶/K) Sputtering 0.12 0.80 0.57 0.57 0.51 — — Rate (Ar 500 eV)

Second Embodiment

In this embodiment, the material of the first electrode 70 is Ti and thematerial of the second electrode 71 is PG. In this case, when the ionbeam processing is performed, PG being the material of the secondelectrode 71 adheres to the surface of the first electrode 70 that usesTi as the material. In the meantime, PG has a property that itsdissolution rate to a solution such as concentrated sulfuric acid,concentrated nitric acid, and a mixed liquid thereof is higher than thatof Ti. Accordingly, PG out of Ti and PG is selectively dissolved by useof this property while performing the cleaning by employing the solutionsuch as concentrated sulfuric acid, concentrated nitric acid, and themixed liquid thereof. Thus, the adhering PG can be removed. In this way,the adhering matter adhering to the first electrode 70 due to the ionbeam processing can be removed by the selective etching. This exerts aneffect of either reducing or eliminating the deformation of theelectrode assembly 109 as with the first embodiment. Moreover, PGparticularly has very high sputtering resistance (a sputteringresistance rate) against the ion beam. Accordingly, PG is less scatteredin the ion beam processing and an amount of deposition of the adheringmatter to the first electrode 70 is reduced as well. As a consequence, acleaning frequency or a replacement frequency of the electrode assembly109 can be reduced.

As described above, it is possible to facilitate the cleaning of thefirst electrode 70 and to extend a replacement cycle thereof by formingthe first electrode 70 and the second electrode 71 from the materialsdifferent from each other, and forming the second electrode 71 from thematerial having higher sputtering resistance than that of the firstelectrode 70. This makes it possible to reduce the number of steps aswell as costs of maintenance.

Meanwhile, as with the first embodiment, it is preferable to form thethird electrode 72 from a material different from that of the secondelectrode 71. Furthermore, it is preferable to form the third electrode72 from the same material as that of the first electrode 70. To be morespecific in the light of this embodiment, it is preferable to use Ti asthe material of the first electrode 70, to use PG as the material of thesecond electrode 71, and to use Ti as the material of the thirdelectrode 72. Thus, the third electrode 72 can be cleaned easily as withthe first embodiment.

In this case, when the thermal expansion coefficient of Ti being thematerial of the first electrode 70 is compared with that of PG being thematerial of the second electrode 71, the thermal expansion coefficientof Ti is greater than that of PG. Accordingly, a difference in thermalexpansion between the first electrode 70 and the second electrode 71 atthe time of the ion beam processing may become larger than that in acase where the first electrode 70 and the second electrode 71 are madeof the same substance. At this time, displacement of positions of theion passage holes provided in the first electrode 70 and the secondelectrode 71 at the time of the ion beam processing due to thedifference in thermal expansion may become a problem. In recent years,the area of the substrate 111 being a processing target has beenincreasing in order to improve manufacturing efficiency of electroniccomponents and the like. Accordingly, the ion generation chamber 102also needs to be increased in size, and there is a tendency that thefirst to third electrodes are required to have larger diameters as well.For this reason, the aforementioned displacement of the ion passageholes is more likely to be problematic.

To improve this problem, it is preferable to form the ion passage holesin the first electrode 70 and the second electrode 71 in such positionsto take into account the thermal expansion in advance particularly inthe case of a processing apparatus for a large-area substrate where thedifference in thermal expansion between the first electrode and thesecond electrode 71 may be problematic. Specifically, at the time ofirradiation of the ion beam, the ion passage holes in the respectiveelectrodes should be designed to move from positions at the time ofnon-irradiation of the ion beam in such directions to coincide with oneanother in a planar direction viewed from a perpendicular direction bythe thermal expansion attributed to a rise in temperature. In addition,the positions of the respective ion passage holes may be set inconsideration of the linear expansion coefficients of the materials. Inthis case, at the time of non-irradiation of the ion beam, i.e., at thetime of non-operation, each ion passage hole in one of the electrodesmay be located at such a position not completely coinciding with thecorresponding ion passage hole in another one of the electrodes in termsof the planar direction.

Although the relation between the first electrode 70 and the secondelectrode 71 is mainly discussed in this description in order tosimplify the description, it is also possible to design a relationbetween the second electrode 71 and the third electrode 72 likewise.Thus, a similar effect is obtained.

Third Embodiment

This embodiment is similar to the first embodiment in that the materialof the first electrode 70 is Mo and the material of the second electrode71 is Ti. Moreover, in this embodiment, at least part of the surface ofthe first electrode is coated (covered) with a material contained in thesecond electrode 71.

As described in the section of the first embodiment, when the materialof the first electrode 70 is different from that of the second electrode71, the substance adhering to the first electrode 70 is subjected to thestress attributed to the difference in thermal expansion. Due to thisstress, there may be a problem that the substance adhering to the firstelectrode 70 is prone to detachment and thus leads to generation of theparticles on the surface of the substrate 111. Accordingly, in the thirdembodiment to be discussed in this section, the first electrode 70 iscoated in advance with the material contained in the second electrode71. In this way, at the time of the irradiation of the ion beam, thesubstance of the second electrode 71 adheres as the adhering matter ontothe first electrode 70 not directly but through the intermediary of thecoated film. In this case, since the adhering matter and the coated filmare of the same substance, the adhering matter adheres onto the coatedfilm with high adhesion. In this embodiment, a Ti thin film is coated onMo which is the material of the first electrode 70. Note that it is notalways necessary to coat the entire surface of the first electrode 70.The coated film at least needs to be formed mainly in a region to whichthe etched substance of the second electrode 71 adheres, i.e., on thesurface of the first electrode 70 opposed to the second electrode 71.

The coated film is formed by various methods. For example, the coatedfilm is formed on the first electrode 70 by conducting variousprocessing methods including CVD (chemical vapor deposition), PVD(physical vapor deposition), plating, thermal spraying, and the like.Particularly from the viewpoint of adhesion between a base material anda coated film, it is preferable to form the coated film by thermal sprayprocessing which can bring about excellent adhesion.

When the coated electrode is cleaned, the adhering matter is selectivelyremoved from the base material together with the coated film, and thenanother coated film is formed again by the thermal spray processing inorder to enable the reuse. In this embodiment, for instance, Ti thatadheres to the surface is removed simultaneously with Ti constitutingthe coated film by using the solution such as hydrofluoric acid as withthe first embodiment, and then another Ti film is formed again by thethermal spray processing to enable the reuse.

As described in the first embodiment, a material having a smallerthermal expansion coefficient than that of the material of the secondelectrode 71 is preferably used as the material of the first electrode70 in this embodiment as well, so as to obtain an effect similar to thatof the first embodiment by reducing a difference between the thermalexpansion of the first electrode 70 and the thermal expansions of thecoated film as well as the adhering matter.

Although only the first electrode 70 and the second electrode 71 arediscussed in this description in order to simplify the description, itis also possible to use Ti-coated Mo for the third electrode 72 as withthe first electrode 70. Thus, a similar effect is obtained.

Fourth Embodiment

In this embodiment, the first electrode 70 in the second embodiment ischanged from Ti to Mo. Specifically, in this embodiment, the material ofthe first electrode 70 is Mo and the material of the second electrode 71is PG. This embodiment can also obtain an effect similar to that of thesecond embodiment. When the ion beam processing is performed, PG beingthe material of the second electrode 71 adheres onto the first electrode70 that uses Mo as the material. As with the aforementioned embodiments,such an adhering matter can be removed by the selective etching.

Fifth Embodiment

In this embodiment, the material of the first electrode 70 is Mo and thematerial of the second electrode 71 is also Mo. However, at least partof the surface of the first electrode 70 is coated with nickel (Ni). Inthis way, at the time of the ion beam processing, the adhering matter isformed on the coated film as with the third embodiment. As aconsequence, it is possible to obtain an effect similar to that of thethird embodiment even though the major material of the first electrode70 is the same as that of the second electrode 71. In addition, Ni has aproperty that its adhesion to Mo is fine. Hence, there is an advantagethat the adhering matter is less likely to be detached.

When the first electrode 70 is cleaned, a ferric chloride solution canbe used as a method of selectively etching the Ni coated film off Mo.Procedures other than the selective etching, such as the coating can beconducted in a similar manner to the third embodiment.

Although only the first electrode 70 and the second electrode 71 aremainly discussed in this description in order to simplify thedescription, it is also possible to use the Ni-coated Mo for the thirdelectrode 72 as with the first electrode 70. Thus, a similar effect isobtained.

Sixth Embodiment

In this embodiment, the material contained in the second electrode inthe fifth embodiment is changed from Mo to PG. Specifically, thematerial of the first electrode 70 is Mo and the material of the secondelectrode 71 is PG. However, at least part of the surface of the firstelectrode 70 is coated with nickel (Ni). In this way, as with the thirdembodiment, the adhering matter is formed on the coated film at the timeof the ion beam processing. Thus, an effect similar to those of thethird to fifth embodiments can be obtained. Meanwhile, as discussed inthe section of the second embodiment, PG has very high sputteringresistance against the ion beam as compared to Mo, whereby an amount ofdeposition of the adhering matter to the first electrode 70 is reduced.As a consequence, it is possible to obtain an additional effect that acleaning frequency or a replacement frequency of the electrode assembly109 can be further reduced.

Although only the first electrode 70 and the second electrode 71 aremainly discussed in this description in order to simplify thedescription, it is also possible to use the Ni-coated Mo for the thirdelectrode 72 as with the first electrode 70. Thus, a similar effect isobtained.

Seventh Embodiment

In this embodiment, the material of the first electrode 70 is PG, thematerial of the second electrode 71 is Mo, and the material of the thirdelectrode 72 is Ti. This embodiment can also obtain an effect similar tothat of the first embodiment. Here, when the first electrode 70 iscleaned, a mixed solution of hydrofluoric acid and nitric acid can beused as a method of selectively etching Mo being the adhering matter offthe first electrode 70 using PG as its material.

Other Embodiments

Although the ion beam etching is explained in the above-describedembodiments as the ion beam processing, the present invention isapplicable to other aspects as long as the aspects adopt processingusing an ion beam, such as ion implantation.

As described above in the embodiments, the first electrode 70 and thesecond electrode 71 provided in the electrode assembly 109 of the IBEapparatus 100 are made from the materials different from each other.Thus, the material of the second electrode 71 that adheres onto thefirst electrode 70 due to the ion beam processing can be easily cleanedand removed by the selective etching that uses a solution having a rateto dissolve the second electrode 71 which is higher than a rate todissolve the first electrode 70. In this way, it is possible to performchemical processing by utilizing reactivity without application of amechanical force, and the deformation of the electrode assembly 109,which has been a problem of the conventional physical processing such asthe blasting, is either reduced or eliminated as a consequence.Accordingly, the product life of the electrode assembly 109 is extendedand the effect of reusability can be thus obtained.

What is claimed is:
 1. An ion beam processing apparatus configured toperform processing by ion beam irradiation, the apparatus comprising: anion generation chamber including an ion generator; a processing chamberin which the processing is performed and a holder to hold a substrate isdisposed; a plurality of electrodes configured to separate the iongeneration chamber from the processing chamber, and to form an ion beamby extracting ions generated in the ion generation chamber to theprocessing chamber, the plurality of electrodes being flat plate-shapedand spaced apart from one another at regular intervals by a gap and theplurality of electrodes including a first electrode disposed close tothe ion generation chamber and provided with a first ion passage hole toallow passage of the ions, a second electrode disposed adjacent to thefirst electrode and closer to the processing chamber than the firstelectrode is, and provided with a second ion passage hole to allowpassage of the ions, and a third electrode disposed adjacent to thesecond electrode and closer to the processing chamber than the secondelectrode is, and provided with a third ion passage hole to allowpassage of the ions; and a power unit configured to apply differentelectric potentials to the first electrode and the second electrode,respectively, so as to accelerate the ions generated by the iongenerator in the ion generation chamber, a positive voltage beingapplied to the first electrode and a negative voltage being applied tothe second electrode, wherein a material of the first electrode isdifferent from a material of the second electrode, the material of thesecond electrode having a higher sputtering resistance than the materialof the first electrode, wherein a ground potential, which is differentfrom the electric potentials to be applied to the first electrode andthe second electrode, is applied to the third electrode, wherein amaterial of the third electrode is different from the material of thesecond electrode, wherein the first electrode and the third electrodeare made of the same material, and wherein a linear expansioncoefficient α₁ of the material of the first electrode and a linearexpansion coefficient α₂ of the material of the second electrode satisfya relation of α₁>α₂.
 2. The ion beam processing apparatus according toclaim 1, wherein the first electrode contains titanium, and wherein thesecond electrode contains pyrolytic graphite.